1. Field of the Invention
the present invention relates to multiple frequency tunable diode lasers utilizing a grazing incidence grating cavity.
2. Description of the Prior Art
various techniques for the simultaneous generation of selectable wavelengths from a single diode laser exist in the prior art. Multichannel grating cavity lasers such as described by I. H. White "A Multichannel Grating Cavity Laser For Wavelength Division Multiplexing Applications," IEEE Journal of Lightwave Technology, Vol. 9, No. 7, July 1991, pp. 893-898.
Another device for this purpose is described by K. O. Nyario, et al., "Multiple Channel Signal Generation Using Multichannel Grating Cavity Laser With Crosstalk Compensation," Electronics Letters, Vol. 28, No. 3, 30 January 1992, pp. 261-263. The device utilizes a multichannel grating cavity laser in which multiple stripes are driven simultaneously.
A single output, variable wavelength device is described by J. B. D. Soule, et al., "Wavelength-Selectable Laser Emission From A Multistripe Array Grating Integrated Cavity Case," Applied Physics letters, Vol. 61, No. 23, 7 December 1992, pp. 2750-2752. In this device, single output/selectable wavelength operation was obtained by blazing a single "output" stripe and injection pumping different second stripes in order to obtain lasing at different wavelengths.
The improvement to the preceding device set forth by Doguntka, et al., "Simultaneous Multiple Wavelength Operation of a Multistripe Array Grating Integrated Cavity Laser," Applied Physics Letters Vol. 62, No. 17, 28 April 1993, pp. 2024-2026, achieves simultaneous multiwavelength operation by simultaneously injection pumping a number of different second stripes together with a single output stripe.
The preceding prior art systems all suffer from the deficiency discussed by M. C. Farries, et al., in "Tunable Multiwavelength Semiconductor Laser With Single Fibre Output," Electronics Letters, Vol. 27, No. 17, 15 August 1991, pp. 1498-1499. Specifically, these devices require a complex semiconductor die. The system of this publication uses an external casing consisting of a fiber optic loop mirror with two output ports fusion spliced to form a Sagnac interferometer.
A publication by G. C. Paden, et al., "Multiple Wavelength Operation Of A Laser-Diode Array Coupled To An External Cavity," Optics letters, Vol. 18, No. 17, Sep. 1, 1993, pp. 1441-1443, utilizes a multiple diode array coupled to a single cavity such that each diode lases at a different wavelength.
G. R. Hadley, et al., in "Free-Running Modes For Gain-Guided Diode Laser Arrays," Journal of Quantum Electronics, Vol. QE-23, No. 6. June 1987, pp. 765-774, presented a numerical model for analysis of gain-guided diode laser arrays.
Further analysis of gain guided (multistripe) diode laser arrays is presented by J. M. Verdiell, et al., "A Broad-Area Mode-Coupling Model For Multiple-Stripe Semiconductor Lasers," Journal of Quantum Electronics, Vol. 26, No. 2, February 1990, pp. 270-279.
The prior art systems require either a complex multistripe semiconductor die or voltage diodes to achieve variable, multiple frequency operation.